Method of molding electric contact rings



J1me 1957 N. M. HARVENDER 2,796,635

METHOD OF MOLDING ELECTRIC CONTACT RINGS Filed May 18, 1954 3 Fl 6. Fl(5. Z.

INVENTOR. NELSON M. HARVENDER A TTORNEYS United ttes Patent IVIETHOD OFMOLDING ELECTRIC CONTACT RBIGS Nelson M. Harvender, Stamford, Conn.,assignor, by mesne assignments, to Breeze Corporations, Ina, Union, N.3., a corporation of New Jersey Application May 18, 1954, Serial No.430,600

1 Claim. (Cl. 18-59) This invention relates to the plastic molding art,more in particular, to the molding of a combination metal and plasticarticle.

Heretofore, in the molding of a plastic about a metal insert by eitherthe injection or transfer molding process, there has been a certainamount of distortion of the metal due to the strains set up in themolding process caused by the differences in the thermal expansion ratesof the plastic and the metal. If it was desired that the metal insert bein the form of a ring and have a planar surface, it was found to benecessary to either machine or grind the article after molding in orderto obtain the desired surface.

It is an object of the present invention to obtain by a simple moldingstep a combination metal and plastic article wherein the metal articlepresents the desired surface characteristic without a machining stepafter molding.

It has been found that the molding strains caused deformation of a metalinsert when a combination metal and plastic article was made in order tobe able to mold a metal part in combination with plastic of either thethermosetting or thermo-plastic type and that it was necessary tocompensate for the deformity of the metal part by a change inconfiguration of the metal insert before moldmg.

One embodiment of this invention is illustrated in the accompanyingdrawing wherein:

Fig. 1 is a plan view of the upper surface of a metal 8;

Fig. 2 is a plan view of the lower surface of a metal 8;

Fig. 3 is a section on line 33 of Fig. 1;

Fig. 4 is a plan view of the upper surface of the molded article;

Fig. 5 is a plan view of the lower surface of the molded article; and

Fig. 6 is a section on line 6-6 of Fig. 4.

Fig. 7 is a cross sectional view showing the article in the mold.

Referring more specifically to the drawing, a metal insert to be moldedin a plastic article wherein it is desired that the metal insert have aplanar upper surface, is shown in Fig. 1, wherein 10 is a metal ringhaving a connector projection 11. The upper surface of this ring shownin Fig. 3 is sloped toward the center of the ring so that the inner edge12 is thinner than the outer edge 13. It has the outer lip 14 and theinner lip 15. This sloping upper surface 16 is not parallel to theplanar lower surface 17 as shown in Fig. 3. The lips 14 and arecontinuous as shown in Fig. 1.

A plastic backing 18 is molded (as shown in Figs. 4 and 5) about thisring by either the injection molding 2,796,635 Patented June 25, 1957ICC process or the transfer molding process using a plastic of eitherthe thermo setting or the thermo plastic type. This plastic ismanipulated at a temperature substantially above room temperaturedepending on the type of plastic. The metal insert 17 is placed in themold 20, 21, shown in Fig. 7 so that the exposed surface of the ring isreceived within the recess in the lower half of the mold 20. The upperhalf of the mold 21 is then brought into position and the plasticbacking 18 is then admitted under the proper temperature and pressurethrough the gate 22, as shown in Fig. 7. This ring when removed from themold takes the shape shown in Fig. 6. The article is removed from themold and cooled to room temperature. Certain well known strains are setup in the article due to the differences in contraction between themetal and the plastic. These strains will deform the finished article ina manner capable of being determined and it has been found if a ringtype article, such as is here illustrated is being formed, that themetal will be deformed in such a manner that the smaller circumferencewill be forced toward the exposed metal surface and the outercircumference forced away from the exposed metal surface. This is shownin Figs. 4, 5 and 6, as resulting in a surface 16 being a planar surfacewhile the opposed surface 17 is now sloping towards the center of thering. This method of molding by compensating for a distortion bystarting with a metal insert that is so prepared that the surfaces willbe those desired after distortion, has heretofore not been known.

The particular application of the broad general invention describedabove applies to contact rings for conveying current from a moving partto a stationary part.

It also can apply to clutch plates or any device where it is desired tomold the plastic about a flat metal insert exposing one surface of themetal and have this surface a planar surface. The electrical contactring so formed must have a planar surface to give satisfactory contactswith the brush and heretofore it has been necessary to machine theseparts in order to obtain the desired surface feature.

While in the above example metal plates have been used as anillustration, it is realized that one skilled in the art can use thisinvention to form any plastic body containing a metal insert as thestrain set up due to the cooling and the diiferent expansion willproduce distortion in the finished article.

What is claimed is:

A process for producing a flat metal annulus having rigidly attachedthereto a plastic backing on one side of said annulus which comprisesforming a metal annulus, the upper side of which has a raised portionnarrower than the lower side, the upper surface of the raised portionsloping towards the center of the annulus with relation to the lowerportion, inserting said metal annulus in a mold with the raised portionpartially seated in a recess in the mold and flowing plastic under heatand pressure around the metal insert to form a plastic backing whichcovers the lower surface and distorts the annulus so that the exposedraised surface is a planar surface.

References Cited in the file of this patent UNITED STATES PATENTS1,186,693 Siggins June 13, 1916 1,241,559 Scheibe Oct. 2, 1917 1,763,653Harvey June 17, 1930 1,907,303 Peterson May 2, 1933 2,307,874 Bilde Jan.12, 1943

